MassGIS Data - MassDEP Eelgrass 1995 and 2001

February 2006

Overview

Seagrass, a form of Submerged Aquatic Vegetation (SAV), serves as important fish and wildlife habitat and assists with storage and recycling of nutrients and the stabilization of sediments. The predominant seagrass found in Massachusetts coastal waters is eelgrass (Zostera marina). The Massachusetts Department of Environmental Protection (MassDEP) began surveying seagrass in the early 1990s and the MassDEP Eelgrass Mapping Project has produced multiple phases of seagrass mapping along the Massachusetts coastline.

This layer contains the combined features from the first two mapping phases of the MassDEP Eelgrass Mapping Project. Phase 1 was conducted in 1995 and included a survey of the entire Massachusetts coastline. Phase 2 was conducted in 2001 and included the entire Massachusetts coastline with the exception of the Elizabeth Islands (Gosnold), Billingsgate Shoals and Mount Hope Bay. The purpose of the Phase 2 (2001) mapping was to determine areas where the SAV resource was decreasing in area and cover as compared to the SAV distribution mapped in Phase 1 (1995). The methods used in Phase 2 (2001) were similar to those used in Phase 1 (1995). One exception to this specification was the change in the delineation of apparent areas of no Zostera within polygons of the resource (i.e. holes). This change in mapping convention was derived from a better understanding of the scientific literature of the dynamics of Zostera beds which describes subtle “infra” movement within beds in response to day-to-day wave action, currents and sand migration, and storm events. Another difference between the Phase 1(1995) and Phase 2 (2001) mapping is that two areas of the coastline, the Elizabeth Islands and Mount Hope Bay were not re-mapped in 2001. The reason for this change is that the Elizabeth Islands are relatively pristine and without environmental stressors to the resource and Mount Hope Bay had no Zostera found in 1995.

The layer is named EELGRASS_POLY.

Methodology

The mapping process involved the following steps:

Acquisition of Aerial Imagery

Photo-interpretation of SAV resources

Fieldwork to confirm Photo-interpreted SAV features

Compilation to Digital Orthophoto Base Map

Acquisition of Aerial Photography: Aerial imagery (Aerocolor 2448 color positive film) at a scale of 1:20,000 was acquired over the period of 1999-2001. Collecting aerial imagery under the proper environmental conditions is critical to successful benthic mapping. The image acquisition mission required collecting data at low tide, during the period of high seagrass biomass from May 15 to August 31, sun angle between 20 and 35 degrees, low water turbidity, and weather conditions of no clouds and winds less than 10 mph. The imagery was ortho-rectified at a resolution of 1 meter with 90% of the pixels accurate to within 3 meters.

Photo-interpretation: The accurate identification of SAV in aerial photographs requires visual evaluation of the fundamental elements of image interpretation (tone, color, contrast, texture and shadow). It also requires extensive experience at ground level in the particular study area. The photographic images of SAV and other benthic images vary in ways that cannot readily be modeled, described or communicated. Training for SAV photointerpretation includes: literature research, discussions with local ecologists and biologists, site visits, overflights in a small plane, and examinations of historical aerial photographs of the area.

SAV are observed best using stereo pairs of photographs and high quality stereoscopic instruments (MassDEP Wetlands Conservancy Program (WCP) uses a Cartographic Engineering Ltd. Model SB 190). SRV polygons are drafted onto overlays fixed to each photograph. Minimum mapping unit is 20 meters. SRV (and other benthic features) in a given area will present a variety of signatures depending upon the bottom sediment, depth, season and haze. Shadows from clouds or trees, turbid water, white caps, or sun glint may obscure SRV signatures in the photograph.

Fieldwork: Extensive fieldwork was required to verify that the photosignature was SAV or some other type of benthic feature (macroalgae, mussel bed, dark sand, shells, rock, or other). SAV can also be combined with any of these other benthic features. Fieldwork was conducted in a small boat using surface observation and underwater observation for which an underwater video camera system was utilized. Field notes were compiled digitally in an onboard computer equipped with real-time differentially-corrected GPS positions.

Attributes

The mapped SAV features from Phase 1 (1995) and Phase 2 (2001) of the MassDEP Eelgrass Mapping Project were combined into a single layer (EELGRASS_POLY). The CODE field was added to specify whether the delineated SAV area existed only in 1995 (95 ONLY) or only in 2001 (01 ONLY) or existed in both years (95 AND 01). The attribute fields for this layer are:

Tool Name: Baynote, Inc. Recommendations

The information below summarizes privacy policy terms related to content recommendations on Mass.Gov and is excerpted from the full Mass.gov privacy policy.

Purpose: Displays relevant content recommendation based on the site usage pattern of all users of Mass.Gov. If Personalization is enabled (the default setting), your personal site usage pattern today and on prior visits to Mass.gov will be displayed to you and will also be a factor in determining personalized relevant recommendations for you.

Data Collected: A random anonymous unique identifier is assigned and tracked for each user of the website. This identifier is sent to our vendor, Baynote, when you view a page, open a document or click a link on Mass.Gov. Our vendor then analyzes the specific content that was viewed and provides content recommendations to similar content that you may find useful. A full description of what data Baynote collects and how it uses this data is available at http://www.baynote.com/baynote-services-privacy-policy/. Please note that the tool uses persistent cookies. These cookies will be Mass.gov domain cookies and not Baynote domain cookies. The cookies will store information related to a user’s Mass.gov Web site usage, including the URL and title of sites recently visited and the random anonymous unique identifier assigned to the user. In general, and as described in more detail in Baynote’s service privacy policy linked to above, Baynote only uses the personalized information it gathers to provide recommendation services and display past usage for Mass.Gov users and will not share this information with any third parties, including advertisers. The information collected will not affect content you may see on sites unaffiliated with Mass.Gov.

Express Opt Out: If personalization of recommendations based on the content you view is not desired, or you do not wish to display a list of recently viewed Mass.gov pages, you may turn personalization off. You can do this by using either the switch located below in this privacy policy or an identical switch located directly above the content recommendations and recently viewed content boxes displayed on the Mass.gov site. Once you turn off personalization, your content recommendations will be based on the overall traffic patterns of all users of Mass.Gov and they will not specifically take into account your own personal usage patterns. If you turn off personalization, information collected by this Tool that is associated with your content usage will be deleted from your cookies, and no further information about your content usage will be sent to our vendor.

Disabling personalization will affect both content recommendations and recently viewed page links. If you turn off personalization, this “off” setting will persist as you browse Mass.Gov and during any future sessions. The opt-out setting is stored in a persistent cookie on your computer. The setting will remain in effect so long as you use the same computer with the same Internet browser. If you delete the cookie that contains the opt-out setting or use a different browser or computer, personalization will be enabled and you will need to disable it again on your next visit, if desired.

For our full privacy policy, please close this window and see the Site Policies or Privacy Policy link in the footer of the page.